1. Field of the Invention
The present invention relates, in general, to a method of producing cermets, used as a material of cutting tools, die material, etc., and, more particularly, to a method of making titanium carbide (TiC) based cermets using TiC based particles, produced through a reaction milling process, thus making TiC based cermets having both a desirably high degree of hardness and a desirably high degree of toughness, while reducing the production cost of the cermets.
2. Description of the Prior Art
As well known to those skilled in the art, the technical term "cermet" is a composite word of "ceramics" and "metal", and is interpreted as a various combination of metal-ceramic materials in a broad sense. In the field of cutting tools, the term "cermet" somewhat limitedly denotes a carbide based material that is made by mixing, pressing, and sintering metal particles, such as nickel, molybdenum or cobalt particles, with titanium carbide (TiC) or titanium carbonitride (Ti(CN)) ceramic phase powders.
A titanium carbide-nickel-molybdenum cermet or the earliest cermet was proposed and commercially used in Germany in the 1920's. These cermets, made of such titanium carbide-nickel-molybdenum powders, preferably have a high degree of hardness, a high degree of oxidation resistance and a high degree of adhesion resistance, but regrettably have a high degree of brittleness, thus being easily broken. Such cermets are thereby rarely used in a roughing process or an interrupted cutting process.
After the 1920's, TiC-(Ta,W)C-molybdenum-nickel-cobalt cermets, made by mixing, pressing and sintering cobalt in addition to nickel and molybdenum with a second or third carbide in addition to the titanium carbide, have been proposed and used. The cermets, made of the TiC-(Ta,W)C-molybdenum-nickel-cobalt powders, have an improved cutting performance in comparison with the titanium carbide-nickel-molybdenum cermets.
After the 1970's, TiC-TiN cermets or Ti(CN) cermets, having an improved toughness and a high degree of thermal stability, have been proposed and commercially marketed.
FIG. 1a is a block diagram showing a conventional process of producing a TiC based cermet. As shown in the drawing, the conventional process of producing the TiC based cermet comprises the steps of primarily mixing metal particles, such as Ni, Co, or Mo particles, with carbide ceramic particles, such as TiC, TaC, or WC particles, while mixing the particles, thus preparing a metal-ceramic particle mixture prior to forming a preform using the metal-ceramic particle mixture. The preform is, thereafter, presintered, intermediate-machined and final-sintered, thus making a desired cermet. In such a TiC based cermet, the hardness and toughness of the cermet is determined by the size of the TiC particles.
However, the TiC based cermet is problematic in that the TiC particles, determining the properties of the resulting cermet, are very expensive and the cost of the TiC particles is further increased as the size of the TiC particles is reduced. Therefore, TiC based cermet tools, having a high degree of hardness and a high degree of toughness, have to be regrettably made at a high production cost and this restricts the TiC based cermet tools from being more widely used in a cutting process.